Hitherto, X-ray image capturing devices that capture images capturing of objects using X-rays, which are a type of radiation, thereby obtaining X-ray images, have become widespread mainly in medical fields. More particularly, interventional radiology (IVR) has become widespread in sites of medical treatment. In the IVR, a person (a doctor) that performs surgery finds a vascular occlusion portion or cancer cells of an object using angiography, and the person treats the vascular occlusion portion or the cancer cells using a balloon or a stent that is inserted into a blood vessel of the object under fluoroscopy. In the IVR, because insertion of a balloon or a stent into an object (a subject person) or control of the balloon or the stent needs to be performed under fluoroscopy, an X-ray image capturing device including a television (TV) system is used. In the above-mentioned IVR, a contrast medium is injected into a blood vessel (for example, a coronary artery) of a portion, which is to be subjected to surgery, of an object, and capturing of a fluoroscopic image (a radiographic image) of the portion to be subjected to surgery is performed. A person (a doctor) that performs surgery treats a vascular occlusion portion, cancer cells, or the like using a balloon or a stent while the person is looking at the captured fluoroscopic image (radiographic image). In this case, in order to carefully look at the portion to be subjected to surgery, a system in which a portion of a fluoroscopic image is specified and in which the specified portion is displayed in an enlarged manner has been proposed, for example, as disclosed in Patent Citation 1 given below.
However, in a case in which a treatment act using the IVR is performed, when only a portion, which is to be subjected to surgery, of an object is displayed in an enlarged manner, it is difficult to grasp a position at which the portion to be subjected to surgery is located on a portion (for example, the heart), whose image should be captured, of the object. Accordingly, there is a probability that efficiency of the treatment act is reduced. For this reason, typically, it is necessary to capture an image of the entirety of the portion whose image should be captured. As a result, there is a problem that the dose of X-rays (radiation) with which the object (a subject person) is irradiated is increased.    Patent Citation 1: Japanese Patent Laid-Open No. 5-260381